We've seen some TA questions about GEA, so we thought we'd share our experience. I apologize if this is not the proper forum.
GEA Tours is a popular alternative to Trains/Buses for getting around the Balkan. My wife and I used them for the Sarajevo to Belgrade (20 Euro/per person), and Belgrade to Timisoara, Romania (20 Euro/per person) routes in early November.
You have to have the right personality to use this service. If you're infinitely flexible, don't have to catch a connection, and are the kind that don't need to have everything confirmed to the minute, this may be your cup of tea.
If you're somewhat of a control freak or like to have all your ducks in a row days before departure, I would go with a train or a bus. If you have to catch a connection, I would definitely use a bus or train.
On our Sajarevo-Belgrade leg, we had emailed back and forth and we thought we confirmed (the night before) that we had two seats on the 11:00 departure (or as close to it as possible) the following day. When we emailed the next day to confirm a departure time, they said they didn't have us down for the morning departure. To be fair, we should have pinned them down to confirm a reservation, but with about 4 emails, I thought I had one. In any event, I assumed responsibility and didn't make a stink. We were placed on the 16:00 departure. We didn't get picked us up until 1730 and arrived in Belgrade at 2230, about an hour behind schedule.
Four days later we used GEA Tours for the Belgrade-Timisoara. When we booked, we again asked for a morning departure. We received an email back indicating they had no morning service, so we asked for an afternoon departure. We learned from our prior interaction and obtained email confirmation of a nebulous afternoon departure. On the evening before the departure date, we received a call from GEA Tours letting us know we would be leaving at 0600 and not in the afternoon as we were previously told. So we just went with the flow and checked out of our apartment early the following day. We were picked up at 0645 the following day and arrived at Timisoara without incident. I will say that the driver made extra effort to contact us. We're from the US and had an issue with our mobile carrier on the departure date. During the morning, the driver called us twice and sent us a two texts to let us know he was on his way. We received one of his texts after he had waited in front of our apartment for 15 minutes or so. We received both voicemails and the other text only after we got on the road. So we're grateful he made the extra effort not to leave us behind, and tipped him accordingly.
So GEA Tours is a mixed bag. The door to door service is as great as advertised. After having to carry heavy bags around for a couple months and finding addresses, it's nice not to have to. Both times we used them, the drivers were pleasant. (We didn't have any border crossing issues as some other posters had.) We didn't find the drivers overly aggressive. The minibuses were nice enough. The emails with the company can be spotty, so you just have to be firm (but polite) about getting confirmation (and it's fairly informal, nothing like you'd receive from an agency booing or the like). Again, I wouldn't use this service if I was trying to get somewhere to catch a connection because you don't need the extra anxiety.
If anyone has specific questions, I would be happy to respond.