Is an RTS+TBS game greater than the sum of its parts? With Sins of a Solar Empire, the answer is: YES.
On its own, the RTS battles in SoaSE are decent if not good. The graphics are nice, and all the usual rock-scissor-paper elements are in place. But you don't advance through ages (and get wildly varied units during the course of a game), nor do many of the techs you research show themselves visually. Many techs are of the "make my lasers stronger" or "increase my population cap" variety and, while important, aren't "Wow!" moments. You can control your units, but the AI is generally competent enough to do this on its own -- it has to be, really, as micro-managing this many units across such huge expanses would be the game's downfall. So for the RTS player, what's in this for them?
Ironclad has said to the RTS crowd: What we don't give you in pacing of and involvement in individual battles, we will make up for in size and variety in decision making. That is, certainly by mid-game, battles often take place across several screens (planets) at once. So while a given battle might be slower and less interactive than a normal RTS, you are usually involved in more than one of them at a time. Thus, the RTS side of the brain is still very much engaged but at a more macro level: When you're not micro-managing a given battle, there are still planets to improve, a rich tech tree to exploit, pirates to kill or bribe, and diplomacy to consider in real time as well. This dynamic creates a certain mental frenzy of its own, which likely would appeal to an RTS player who likes to keep busy.
TBS
For the hardcore TBS player, keep in mind that you can pause the action and issue orders. You can also choose a slow tech rate or pick any number of variable (map setup, etc.) to ensure any kind of pace you'd like. The question, then, is: Did Ironclad leave enough of the Strategy when they decided to join forces with the Real Time? Indeed, they have.
Not unlike Civilization or any other brand-name TBS game, optimal build order of planetary improvements, research, etc., is still king in this game. In fact, the economy in SoaSE is so influenced by things such as logistic caps and limited resources that figuring out how best to squeeze every celestial credit out of every phase of the game is critical to your success. And unlike many RTS games where this boils down to putting as many "villagers" on as many resources as you possibly can, here you have to carefully weigh, for example, whether or not your cash on hand is best spent on two trade outposts or on that technology that increases your resource rate? But somebody has just put a bounty on your head, so maybe that cash is better spent right now on making your enemy a more profitable target? Oh, you might also want some planetary defenses or even a ship or two. Suddenly many of the many simple decisions that take place in a normal TBS become quite complicated -- not just because of the RTS nature of the game but because Ironclad has designed the game this way. This IS a thinking-man's game! Fielding a large, modern fleet is a success story in itself and requires some very careful thinking that will likely appeal to the TBS gamer. Such careful thinking will, in fact, often result in a more diverse unit set, with more updated weapons, and this will often carry the day when it comes time to battle. Fast reflexes is not the point here.
SUM
I enjoy both RTS and TBS. RTS fit my lifestyle better before I was married and had two kids, so I tend now toward the TBS side. I was worried that SoaSE would somehow ruin both by trying to be both. All I can tell you is that I spent the last two days putting 12 hours in each on SoaSE. Yes, I took two days off from work as these were weekdays (and I wanted to be home when the kids were at school!). I haven't done that in years and years. I am also thinking about strategies as I catch a few moments at work. I'm thinking, too, about all the maps and scenarios that I haven't yet tried or the higher level AI difficulty I am pained to think about.
Is the game perfect? No. The Normal AI will often leave neutral resources unclaimed and will ignore your claim on these resources even when it could easily take them. This should be fixed! The AI often calculates the odds of a battle and, if it can't win rather easily, runs away. This is good on the one hand, but when it runs to a better-defended planet (with stationary defenses such as missile platforms, etc.), it doesn't draw you in to those defenses where it could carry the day. It often runs away, leaving those stationary defenses open to attack. This also needs to be addressed! However, forcing a losing match up on the AI without also opening your own planets to an inevitable counter-attack by a third party (not to mention pirates) is HARD. I'm assuming more than a 1v1, here. A free-for-all (FFA) on something like the Centrifuge map is anything but easy to win, so I guess it's just a little disappointing that the AI doesn't play a little better when the odds are against it.
Finally, while many reviews have focused on the lack of a campaign, most campaigns are over-scripted and don't translate well to what the real thing is like anyway -- single player or on-line. Instead, Ironclad clearly put development time and resources into things that, to me, really matter: Good (if not perfect!) AI, tons of maps and scenarios, and just an underlying gaming dynamic that sucks hour after hour from your life as you are convinced you've finally tipped the balance in your favor only to feel yet another counter-strike hitting you at a weak spot, forcing you to rethink your next moves. Or to start fresh, "this time" convinced you've got the right balance. "This time" is looking to provide me with months of some of the best gaming I've experienced in a long time.