I've been on the Lufthansa flight to Frankfurt quite a few times this year and it's always been busy.
Looks like it's a Embraer E90 in the schedule starting tomorrow, so slightly more capacity (and a more comfortable experience in my opinion) than the CRJ900 that has been working the route so far.
I have just done LH to LEJ via FRA return and yes the extra seats on the E190 must be good as the CRJ900 was full on way out and very nearly full coming back! But I must say personal preference is for the CRJ900! It really could do with going double daily, Especially when BA first choice for cutbacks is domestic!