I did Honours in BABS last year (2007) and personally I thought the school actually supports you quite well throughout the year. It is an intense year of scientific training and it literally pushes you to the edge and while you're doing it you feel like it's not worth it, but at the end of it all when you look back you realise you've learned an incredible array of scientific and writing skills that you would not have been able to gain from the previous 3 years of undergraduate learning. Every once in a while I look up to my bookshelf and I see my hard-bound 70 pages Honours thesis, everything comes flashing back - the literature review, the presentations, the interviews, the thesis, the lab work, the stress associated with failed experiments - and you often get emotional and think "how the hell did I get though it all?" I can honestly tell you I'm a better scientist now and I wouldn't be able to become the scientist I am today without doing an Honours year.
I suppose you do get "more" time by entering mid-year with the Christmas break in between but in fact, most facilities close in BABS anyway during this period. You can't do sequencing and access to the Ramaciotti centre/the postdocs who help you in your projects go on holiday etc. Most students work on their thesis throughout the year not at the end anyway so I don't think it will make a huge difference which session you enter your Honours year.
The best advice I could give to future Honours students is that pick a supervisor who you can work with. The project is secondary and can often change depending on funding and how you progress throughout the year.