So I downloaded Sins of a Solar Empire beta and I played it straight for almost 12 hours (finishing one game on a medium galaxy...phew) and although the RTS/4E formula is potentially irrestible, the big problem is balancing scale vs. manageability. I can't imagine playing more than a couple hours of an RTS in a multiplayer setting; although the slower pace and longer game is appealing (C&C3s 'over in 5 minutes' turned me off) there is a limit. There's a reason why most 4E games are about the sandbox. Balancing the running of your empire with the tactical RTS elements is the key imo.

What's good:
-The UI. Although there are a few tweaks that could be added, I had little problem managing my relatively large empire and fleets. The collapsable menues with the pips are genius. Being able to select all ships in a system while zoomed out is good. Navigating a game of this scale in realtime was inevitably going to be tricky, and I think Sins does a great job.
-Capital ships are fun. I like them as "hero" units, and they all seem pretty distinctive and useful. It does seem odd that they're easier to get than certain cruisers, though.
-It's a pretty game. My ships look cool.
-Basic concept of economy seems fine.
-Bounties are a nifty way to create tension in an FFA (or 3+ sided) game.
-I like the FEEL of the space. Battle taking place around solar systems, choke points, and gravity wells creates a kind of 'terrain' often missing from these kinds of games.

Needs tweaking:
-Unit speed, particularly in the gravity well. I am convinced that a good part of the reason the game takes so long is because ships take forever to move anywhere, especially compared to how relatively quick it is to build, conduct research, etc. Also, slow speed contributes to the next problem.
-More tactics in the RTS battles. Ships are overall too slow (except Kodiaks using intercept) for maneuvers to be meaningful. Besides mashing my capital ship abilities at a time that's not totally stupid, there's a tendency for me anyway to just dump ships in and let the AI figure it out once we get to any sizable battles. Also, a lot of battles are conducted at a level of zoom where everything is represented by symbols. What's the point of all these gorgeous ship models if when I'm actually playing the game all I see are blue squares?
-Culture lasts too long. Once I've destroyed every structure and ship my opponent has I should not have to coordinate simultaneous invasions of half their former empire. Although I like this in concept as a kind of 'countercurrent' to an invading fleet, write now it's simply too extreme.
-Allegiance penalties in a large empire. There needs to be more ways to mitigate this. 100 percent culture is listed as giving 10 percent allegiance. This is great for the planet 3 jumps away from my homeworld, but for a planet in another system it barely matters. Some of the tooltips suggest that you can have a capital in each solar system, but when I tried to do this it simply switched my capital. Having one 'capital' in each solar system would definitely make a difference.

'It's beta, I forgive you':
-AI is not very smart, but as game balance itself is still being worked on I'm not concerned.