No guilt- except when one of the boys is ill and I'm trying to manage them and work.
It's not a big issue as my boss has a good attitude towards family, and DH usually works shifts, so we usually manage quite well, but there was a period earlier this year when work was really difficult (not my boss), all three boys had colds and then sickness bugs and then colds again (just before and after half-term) and DH is not currently working shifts and for the first time in 12 years it was really really difficult to manage, and then I felt guilty - both about the boys and work. And although it was unfortunate some of the illness fell over half-term, when I had leave booked, it helped to deal with the sickness.
Other than that - No, we discussed it and I made the decision to go back. I work part-time flexi hours which generally fit quite well for us as a family. Going back to work helped to keep my sanity during the early years, so was important, apart from the financial aspect. We were lucky with childminders too (grandma then two v good friends).
Do feel overstretched sometimes.