Above 25" or so, I'd demand 2560x1600 (WQSVGA) or similar for day-to-day computer monitor applications, but then I find anything less than about 130DPI objectionable on an LCD. I'm currently rocking a 15.4" 1920x1200 (WUXGA) - that's about 150DPI!
Note that 27" diagonal at 2560x1600 (16:10 aspect) is ~111DPI, which is barely above "Windows standard" from old school blurry CRT days of 96DPI, and this is the highest resolution you're likely to find.
27" diagonal at "Full HD" 1920x1080 (16:9 aspect) is only ~82DPI, which is actually less than "Windows standard", so things would appear comparatively grainy and blocky (or just bigger) to the old reference.
Gotta remember, television resolution has always been fairly low compared to computer monitor uses. There's actually an xkcd strip about this:
http://xkcd.com/732/A 27" 16:9 is probably too big (due to the width) for my taste in a PC monitor, anyway, but you may be fine with it, especially if you just want everything to be "big". I find things that wide tend to exceed my physical field of view at normal monitor viewing distances, which causes me to have to shift my eyes a lot or (worse) pan my head just to use the monitor.
A 27" 16:10 might be OK (though again I'd want very high res at that point since the pixels start getting too big), but I suspect I'd still personally find it too wide. I have some 24" 16:10 CRTs that seem to be about the biggest I'd normally want (I use them for games and such, but I don't like them as much for office/work use).