I hiked a circle around Manaslu in fall 2008 starting at Arughat Bazar, ascending Samdo and Larkya north peak (6056m), passing over Larkya pass and going back through the Dudh Khola valley finally meeting the Annapurna circuit trail.
This was a commercial expedition by German amical alpin. There is nothing serious to say against the organisation except some minor misfits.
This was the first commercial expedition I "booked" in advance. Our group was 12 people strong, coming from Germany and Austria. Amical hired an arrogant mountain guide with a serious lack of social competence, who showed his quality on the one day climbing Larkya north peak, but was totally needless to me during the rest of the travel.
I never did anything with a guide before and didn't travel with a bunch of people I wouldn't know before.
Comparing this with other trips I've done in the past I can resume that it's a lot more fun organising and travelling on your own or in a small group of members that know each other before and go for similar goals together.
Private expeds have a smaller chance to run perfect all the way through, but they are definitely a deeper experience to me, than comercial trips like this one.
Anyway there were enough moments to enjoy away from bugging teammembers or our superhero 8k-guide.
The valleys around Manaslu are still very natural and will stay like this for at least some years until this area also becomes a popular one. The route offers all kind of variation nature has to give since it starts off at 530 meters above sealevel and rises over 5000 meters when passing Larkya pass. Vegetation changes often and even at higher stages very surprisingly. People are friendly and it's good to go through an area that tourism hasn't captured yet.
This trail is perfect for acclimatisation as it rises very slowly day by day following the Budhi Gandaki river all the time. I had absolutely no problem with altitude. Except of a headake on the summitday my body felt fine for 22 days.