I so agree with decmum's point about the tone and language of GF - a judicious bit of advice from the publishers would have made the books so more palatable.
I used ttclb for DD1 (now 3) with a lot of success. I am a very structured person, so it appealed to me to have something to follow. But, being postnatally hormonal and with my life having changed beyond all recognition, I did beat myself up when things didn't happen to the minute.
Eventually I gained confidence in interpreting my dd's needs, and began to go with the flow a bit. I realised that one missed nap or poor feed doesn't break the good routine habits your baby has developed.
With DD2 I'm finding it more difficult to 'do' Gina. I note that there's really not much advice given on how to balance the needs of the elder child, or manage them at the same time as the new baby. For example, some days we can't do a lunchtime sleep because I have to collect dd1 from nursery slap bang in the middle of it. Hoiking dd2 in and out of car sleeps doesn't make for a good nap! Also, bathtime and the quiet wind down for DD2 is virtually impossible unless DH is around to manage teatime tantrums.
My advice kbaby would be to take the general principles - feeding as much as possible between 7am and 7pm, limiting the daytime sleep to the totals mentioned in the book (but not worrying unduly about when these happen), the 2 hour awake time to manage overtiredness, blackout blinds to manage early morning waking and a certain amount of darkness for daytime naps (but not always in the dark, otherwise travelling and day trips become hard!).
Don't beat yourself up about the detail though, and perhaps give yourself a few weeks (or even months) to get to know your baby and his / her patterns first. Don't think that you have to do it from day 1 otherwise the whole thing is doomed - this is the quickest way to get yourself stressed out. Although dh and I were very pleased to have our evenings to ourselves from about 3 weeks, we do sometimes look back on our experiences with dd1 and wish we'd been a bit more relaxed about things. Maybe this is with hindsight though - at the time we felt more relaxed than when we weren't doing a routine!!
Good luck with your baby - enjoy it and be confident that you will know (or will work out) what they need!