My dad and I took three tours with Traventuria and had an excellent time on each one. Each day was easy, relaxing, enjoyable, fun, and very informative. The tours are very personalized, the guides are great, and the company is flexible. For example, my dad and I wanted to go to Belogradchik Fortress, which is not on one of the normal tours with the company, but it was very easy to arrange a trip there anyway. Similarly, our last tour was meant to be a hike through the Rila Lakes; unfortunately, the evening before our tour a cold front blew through and the day dawned with freezing rain. We decided rather late the day before that we didn't want to do it, but unfortunately had no way of contacting Traventuria so late. That morning, when our guide came to pick us up, we asked to change the tour, and it was completely fine, no problem at all. Great, flexible people in charge of the company.
Our guides themselves were also awesome (we had tours with both Orlin and Rusi). Examples of the amazing things they did:
Guiding us on an impromptu hike when we expressed it might be fun to hike for a little while
Clearing away the branches on the trail in front of us while on the hike!
Offering to take pictures of us all the time without us having to ask them to
Knowing which gas stations had clean bathrooms and stopping there
Knowing the back routes to the important sites which avoided traffic/had more beautiful scenery
Offering to call ahead at the restaurant and place my order when I indicated I wanted a dish that he knew took a while to prepare
Taking the time to mark on our city map restaurant recommendations for Sofia when we indicated we were having trouble finding a place to eat
In addition to doing all this, both guides were very knowledgeable, not just about history, but about little quirks about the places we were visiting--they knew which restaurants were good, which place offered the best wine tasting, what was good at what restaurant, etcetera.
I would definitely recommend this tour company. Not only are the guides exemplary and the company flexible, but unless you read Cyrillic, you'll want a guide escorting you around Bulgaria, and you can't find any better than the ones at this company.