Thought I'd list a quick update. Had my first gig with my in ear system last night. I had my kemper going directly from the monitor out into the left channel of the my Shure PSM 300 setup. My plan was to have the sound guy run me a line from the board into the other right channel of my Shure system. I was going to rely on getting a mix of all the vocals (especially my own) and some keyboards from the sound board, then mix my guitar signal in as needed with my unlinked "master volume" monitor out. There are only 2 of us using in ears so we dont have a "band" setup...just our own small rigs.
First problem came when sound guy was running late. He was scrambling to get us ready to go. Then, the only "cable" he had to give me for the feed to my transmitter (Shure) was an XLR. The Shure takes 1/4 in plugs. I figured "no sweat"...I'll just grab my direct box and run it into that and then to my Shure. The XLR he handed me was a male end....which was the same as what my direct box had! Luckily...our keyboard player (only other guy using in ears) runs into the same problem and had an extra female to female adapter so I could plug that into my direct box and then plug in the sound mans cable. Final problem came when we really didnt get any kind of sound check so I just had him throw some vocals in my ears without having much time to do any mixing or much level setting.
Started the show and my first impression for the first 3-4 songs was "WTF am I doing this for!". It was so weird and disconcerting that it really threw me off. I was adjusting my guitar level to try to get a decent mix but it was very very odd and definitely affected my performance. After awhile I started to get used to it but was never "comfortable" all night. The kicker was all of sudden with about 30 minutes left in the show my in ears just die. Nothing. Luckily there was some guitar coming through our vocalists monitor so I was able to pop my in ears out and at least hear "something" of what I was playing. Turns out the battery in the pack ran out. WHAT? It was essentially a new battery. I had it on for maybe 30 minutes at home testing the system out and turned it off during the one break we'd had. Unceremoniously had everyone wait while I got 2 new betteries and threw them in the pack and started back up again.
Long story short. (too late I guess)....by the end of the night I was used to it enough where I see the value. But there definitely is a hassle factor and a learning curve associated with this. Learnings are to come any kind of connectors that I may need and to make sure I have extra batteries sitting out. the band is "talking" about potentially getting a full in ear system. If we do...that will make life much easier (other than I'd have to haul the friggin' setup with me!).
The higher-end systems all use XLR setups, with my Sennheiser G3 system having both XLR and 1/4" capabilities. I would recommend something like that for your next setup. As for batteries, yup I have had that happen (only once to my knowledge). If you're going the rechargeable route (like I do), spend the extra few dollars and get the Panasonic eneloop pro series batteries/charger. Worth the money for the reliability, plus they actually retain charge if left sitting, unlike most cheap duracell variety rechargeables.
I second letting FOH run 1 line into your IEM receiver and mixing EVERYTHING from aa monitor mix (i.e. not going L-kemper R-mix on your unit), but just my $0.02