Wow, there are lots of options to do this! One that hasn't been mentioned is the Ensembl Genome Browser. The positive would be the ability to compare your gene models to Ensembl annotation along the genome. For example, in this view:
Click 'Manage your data' at the left. Either upload a GFF file to Ensembl using the 'Upload data' option at the left of the menu, or use 'Attach URL' to attach your file without uploading it to Ensembl. In both cases, you will be able to view your gene models along the genome, and turn on or off other data tracks.
If you need any help with this option, give it a try or ask our helpdesk to guide you. helpdesk[?]ensembl.org