This was something I've wanted to build almost as long as I've been playing D&D. There are a handful of companies that make some pretty awesome dedicated gaming tables but I specifically wanted to build one, not just own one. Fortunately I had 3-4 months to plan out exactly how the whole thing would go together so there weren't too many surprises. In fact the only "problem" that's come up was due to a copying error when I was making my cut list. I'd modified the draft at one point and somehow the cut list didn't get updated so the lips on the "short" sides of the table wound up being 59" when they should've been 61.5". I'll print off some corner caps to fix that problem though.
I tried to pick the straightest bits of lumber I could manage, particularly the maple boards I was using for the lips but in the ~10 days the lumber was being stowed and shuffled around a lot of it developed a bit of warp. Not enough to compromise the structure but enough so that the lips don't quite line up as nicely as I'd like. More screws and brackets will probably fix that.
The table is 5' wide and 8' long with a 3" inset for our map. I sanded down the cut-outs for the inset so they could serve as a cover. It's nice since the grains all line up and look proper purdy. A 2x3' slab of 3/4" ply is heavier than the covers really need to be though so I'll be doing some lightening with a forstner bit somewhere down the road. I also have a nice dragon design courtesy of my wife to burn into the covers.
Because the frame under the table doesn't extend to the edges I was worried it might sag over time. The lips are meant to mitigate this somewhat (since they double as a rigid frame) but I added a couple of supports on the catty-corner edges. It's nice that they can double for storage to keep all my DM supplies and books handy. The two "unsupported" corners seems pretty solid so far but if they develop any noticeable sag over time I can knock out another pair of shelves to shove under them.
All in all the table might not be "perfect" (yet) but we've been making good use of it and it works really well for our games. Having the inset actually makes it easier to reach across the map to move minis about and all that surface area means nobody's crowded. There's ample elbow room to squeeze in character sheets, books, and cheezies.