If you are looking for features built in I would definitely look at the top WP themes on themeforest.net. You get a lot of bang for your buck with these themes and most are still highly customisable to allow for flexibility of clients. The good ones are regularly updated too, I'd stay away from anything that isn't from an elite author unless they have a good track record outside of the network. Many use sliders that are touch compatible and for the money you get a very full package. They have their limitations but if you know what you are doing a child theme and a bit of CSS will take you a long way.
From that list I've worked with: Modernise, Striking, Mayashop, Udesign. They've all been easy to set up with mostly good to excellent documentation.
These authors do a great job of maintaining compatibility across browsers so really you end up paying for someone else's work.
I've had mixed results with some of the other companies that 'specialise' in WP themes. They've often been far less impressive and feature-rich but marketed more aggressively so you can end up thinking they will do more than they can. Check the descriptions very carefully as they are often very cleverly worded from some of these companies. While themeforests policy is non-commital to support, all of the authors that know what they are doing have support in place.