For DRM-free comics, there's nothing better than Chunky Comic Reader for iPad. It has all the features you'll need, plus it provides the best cloud-syncing functionality for your collection.
Hit Chunky's official page for the full list of features.
The options for DRM-free material is a little shaky (I trust you secure your comics legally), but today's best publisher -- Image Comics -- has your back. As do Brian K. Vaughan and Marcos Martin.
Keep your collection synced to Google Drive and/or Dropbox and use Chunky to access it at all times.