Haven't ridden a bike I haven't built myself (well, "assembled" myself at least, I've not built a frame yet) in errrr... About 12 years! Even the couple of "off the shelf" bikes I have bought in that time have been totally ripped apart, and had most of their components changed to suit my tastes from new (and unused bits sold on ebay in general).
Regarding tools wise, well it really depends how much of the bike you are "building" really. If we're not including wheels, and you're prepared to go to a bike shop to get them to press the headset in and cut the fork steerer, then you can significantly cut down on tools required. You should need the following.
Phillips and Flatblade screwdrivers
BB removal/insertion tool (depends what cranks you're running as to which one you need)
Cassette Lockring tool
Rubber Mallet (yup, you will use it, just don't use it too much!)
Quality cable cutters (can't stress enough do not skimp here, cheap ones are CRAP, Park ones are worth their weight in gold)
Some decent bike grease
And that is about it in truth! You may need a Torx bit for disc bolts possibly (if they're not allen key fitting), but that's about it otherwise. Headset presses are really only for people who build LOTS of bikes, or have a CK headset. If you're using a headset worth closer to £10 than £100, just use the block of wood and rubber mallet technique, though be careful and ease it in, don't try to whack it clean in in one go!
Incidentally, try Aldi/Lidl for bike toolkits. I picked one up from one or the other last year, it had pretty much everything you could ever need to build a bike with in it, and cost me about £16 all up! Ridiculous. Ok, it's not Park stuff, but it's all usable, and it's survived plenty of use by me so far.
Oh, and don't ask why, but however long it takes to build a bike, it usually takes as bloody long again just to setup the bloody front mech on it. I hate them, they require such perfect setup (well, they do if you're a perfectionist like me) which is not easy to achieve necessarily, always a massive PITA!
Anyway, Once you've done a couple of bikes, you'll be onto building your own wheels next!