Making the leap to Design/Engineering (looking for advice)

I'm currently at the crossroads. Been in the field about 6 years.

Currently in Operations where I am relied upon to identify/resolve complicated issues and implementations. I work closely with our engineering/design team as well and have the respect of pretty much the entire team.

Some positions are opening on that team and I'm basically a shoe-in and have been encouraged to apply, for what may be a 20% raise, but no overtime. It's still a significant increase over my gross income with OT. Current boss is also willing to give me a pay increase if I stay(no mention of what amount).

Most of the work I do now is enjoyable - including the stuff I work on with the Design team. I also enjoy troubleshooting when stuff gets really complicated. Some of the work is really not enjoyable, lots of weekend implementations in the DC or WAN Edge, cut-overs at small branch offices every Friday, on-call rotations, etc.

I'm sure people here have made similar moves (inter-company or not), I'm curious what it was like - if there were any challenges or things you did not expect afterwards.

Any advice would be very much appreciated.